[chris_ab]

"In their case, perhaps a long rope tied from their waists to the car door would be a better "guidance system". "

What you refer to is called Orienteering and, specifically, a String Course for those 4 to 7 years of age.

The string course is a short orienteering course which is marked by a continous ribbon or yarn.

Same link: http://www.us.orienteering.org/OYoung/StringO.html

Anyhow, I've done some of this, Orienteering, it's fun, trying and a good exercise...

What is really cool about the sport is it can be done while running or walking. Also, people of all ages do it - I've had a 65 year old guy run by me at a full sprint.

[Redcloak]

Actually, I was thinking more of something more along the lines of a long leash so that they could only wander off a short distance. Hopefully, they could follow the rope back to their vehicle on their own. Otherwise, "rescuers" could simply pull on the rope and drag them back to safety.